In the treatment of radioactive liquids waste it is advantageous to employ vaporizing techniques, since the radioactive contaminants of the liquid are in general non-volatile and can to a large measure be disposed of in the liquid concentrate remaining after such liquid is vaporized. Advantageously, the vapor resulting from the evaporation operation is then condensed for disposal by being contracted by an atomized liquid.
One general technique of this type is shown e.g. in U.S. Pat. No. 3,480,515, issued to R. W. Goeldner on Nov. 29, 1969.
Unfortunately, conventional evaporation techniques of this type are limited in effectiveness by the fact that radioactive droplets of small diameter from the incoming liquid to be purified are unavoidably carried along with the vapor from the evaporation stage, and serve to impose what has heretofore been an irreducible minimum concentration of radioactivity in the final product distillate.
The present invention has as its main object to provide a relatively simple process for vaporizing radioactive liquids and for avoiding the problem indicated above. This distillate obtained by the process has a substantially lower radioactivity than the distillates obtained by the vaporizing installations of the prior art. This result is achieved in the process of this invention by employing a two-step vaporization in which the vapor exiting from a first vaporization stage is condensed by means of liquid obtained by recirculation from a second vaporization stage and the thus formed mixture is conducted to the second vaporization stage. A portion of the liquid mixture resulting from the condensation of the vapor from the first vaporization stage is separately vaporized in the second vaporizing stage. The vapor from the second vaporizing stage is then condensed to form a highly radioactive-free product distillate.
Advantageously, a portion of the liquid mixture present in the second vaporizing stage after such last-mentioned evaporation is recirculated to the first vaporizing stage to further reduce the radioactivity of the final product.